Increasingly stringent emission regulations require diesel engines to use necessary after-treatment purification devices while using clean fuel and in-machine purification. The particulate filter (DPF) is the most commonly used after-treatment technology to deal with PM emissions.
The micropores of particle traps are usually micron-sized, which is much larger than soot particles. Therefore, the micropores cannot directly play a purification role, but through other mechanisms, including diffusion mechanism, interception mechanism, There are four types of inertial collision mechanism and gravity deposition mechanism.
The diffusion mechanism means that after trapped particles appear in the flow field, the trapped particles have a convergence effect on the remaining particles, causing a concentration gradient in the distribution of particles, which in turn produces diffusion and transport of particles, and ultimately causes diffusion and capture of particles.
The interception mechanism means that particles with a diameter greater than or equal to the diameter of the pores of the filter element are captured when they approach the filter surface.
The inertial collision mechanism means that when the exhaust gas flows through the micropores, the streamlines are curved. However, because the mass of the particulate matter is much greater than the mass of the gas micelle, it hits the filter surface of the filter element and is captured.
The gravity deposition mechanism refers to the phenomenon that particles are collected close to the filter surface under the action of gravity. However,
Due to the small mass of particulate matter and the fast exhaust flow rate, the influence of gravity deposition is often ignored.
During the working process of the DPF, the nature of the particulate matter, exhaust flow rate, temperature, DPF specifications and material characteristics have an important impact on the collection efficiency of the DPF.
